The present invention relates to an apparatus for measuring the flow rate of refrigerant in a refrigeration cycle.
In, for example, article 3.2.2 of "Method of Refrigerant Flow Rate" in annex 1 of JIS B 8615-1979, an apparatus for measuring the flow rate of refrigerant in a refrigeration cycle is proposed wherein the flow rate of pressurized liquid refrigerant is directly measured by of a turbine-type flow meter disposed between a condenser and an expansion valve.
In general, the refrigerant flow rate measuring apparatus such as the turbine-type flow meter designed to directly measure the flow rate encounters problems in that the size of the apparatus is impractically large and that presence of many movable parts impairs the reliability of the apparatus during the long use, particularly when the apparatus is subjected to vibration. Therefore, this type of apparatus could be used only in the cases where there is no substantial restriction in the space and where the frequency and condition of use are not critical, as in the case of, for example, an experimental plant.
Accordingly, an object of the invention is to provide a small-sized refrigerant flow rate measuring apparatus which is capable of sustaining a long use even under severe operating conditions.
The invention is based upon such an idea that the flow rate of a fluid in a pipeline can be calculated from the opening degree of a valve disposed in the pipline and the pressure differential across the valve. This basic idea is reported on p 92 of Transactions of the Japan Society of Mechanical Engineers, part 2, vol. 34, No. 257 (S43-1).
More specifically, in order to achieve the object set forth above, the present invention provides a refrigerant flow rate measuring apparatus comprising: a high-pressure side pressure detecting means for detecting the refrigerant pressure at the upstream side of an expansion valve; a low-pressure side pressure detecting means for detecting the refrigerant pressure at the downstream side of the expansion valve; an expansion valve opening degree detecting means for detecting the degree of opening of the expansion valve; and a computing means for determining the pressure difference between the high- and low-pressure side pressure detecting means and for computing the flow rate of refrigerant in the expansion valve from the square root of the pressure difference and the output of the expansion valve opening detecting means.